Bill McKibben
Bill McKibben wrote the first book for a general audience about climate change, The End of Nature, in 1989. He spent three days in jail last summer for protesting the proposed Keystone Pipeline.

A year ago, 1,253 Americans were arrested outside the White House while protesting the proposed Keystone Pipeline, which would run from the tarsands of Alberta to the Gulf of Mexico. Liberating that pool of carbon would, in the words of NASA climatologist James Hansen, mean it's 'game over' for the climate. Mitt Romney has promised that, if elected, his first act would be to approve the project. Barack Obama hasn't said one way or the other what he'd do, which holds out some hope, anyway.